As the most useful process for the production of a 13,14-didehydro PGE among the prior art processes, a process is disclosed on pages 3 and 4 of WO 92/18472, in which the .alpha.-chain of PG is introduced by a conjugated addition reaction using an organic copper compound.
However, since the above process is an anionic reaction, an organic copper compound, which has a reactive hydrogen atom-containing substituent such as free carboxyl group, cannot be used in the reaction. Also, because of an anionic reaction, the organic copper compound cannot be prepared easily and a side reaction is apt to occur at the time of the s-chain introduction, when the starting material is a compound which contains the following groups and the like as its partial structure; ##STR2## which is apt to cause .beta.-elimination; ##STR3## which is apt to cause Michael addition: or ##STR4## which easily becomes allene. Further, this process has another disadvantages in that it is necessary to prevent contamination of water and oxygen when the .alpha.-chain is introduced and it generally requires a very low temperature. In addition, it requires a number of steps after introduction of the .alpha.-chain until its final step.
The object of the present invention is to resolve the aforementioned problems involved in the prior art and hence to provide a process for the production of intermediates for use in the production of an industrially advantageous 13,14-didehydro PGE.